1. Field of the Invention
The present invention relates to an ink jet recording apparatus for outputting characters, images, and other information on a recording medium, a method for determining reduced ink remains of the ink jet recording apparatus, and an information processing apparatus using the ink jet recording apparatus as its output means, such as a copying machine, a facsimile apparatus, a printer, a wordprocessor, and a computer.
2. Related Background Art
Recording apparatuses to perform recording on a recording medium, paper, cloth, plastic sheet, or OHP sheet (hereinafter just referred to as a recording sheet), have hitherto been proposed with various recording methods, such as wire dot, thermosensitive, or ink jet in the mode that its recording head is mountable.
Of these methods, the ink jet is one of the non-impact types where ink is discharged onto a recording sheet to which it adheres directly in lower noises. By the formation methods of ink droplets and methods of generating discharge energy, this method is roughly divided into a continuous method (including charged particle controlling, and spraying), and on-demand method (including such as to use piezoelectric, spark, or bubble jet method).
The continuous method is such that ink is continuously discharged, and only needed ink droplets are charged. The charged droplets are allowed to adhere to the recording sheet while others are discarded. In contrast, the on-demand method is such that ink is discharged only when it is needed for printing and, therefore, no ink is wasted without staining the interior of the apparatus. Also, the on-demand method is arranged to start or suspend ink discharge as required. Consequently, its response frequency is low as compared to the continuous method. This lower frequency is compensated with an increased number of nozzles in order to materialize a higher recording. Therefore, most of the recording apparatuses currently in use are of the on-demand type. Since it is possible for a recording apparatus provided with an ink jet method of the kind to execute recording operations in high density at high speeds, this apparatus is utilized and practically adopted as an output means of an information processing system serving as a printer for a copying machine, a facsimile apparatus, an electronic typewriter, a word processor, or a work station, or adopted as a handy or portable printer provided for a personal computer, a host computer, an optical disc device, or a video apparatus, for example. In such cases, each of the ink jet recording apparatuses is arranged in accordance with the functions, modes of use, and other characteristics of the respective equipment for which each of them is adopted.
As an ink jet recording apparatus in general, it comprises a carriage having recording means (recording head) and ink tank mounted thereon, means for feeding recording sheets, and means for controlling them. Then, a recording head, which is capable of discharging ink droplets from a plurality of discharge ports, is arranged to scan serially in the direction (main scanning direction) perpendicular to the feeding direction (sub-scanning direction) of a recording sheet, while the recording sheet is intermittently fed in an amount equal to the recording width at the time of the recording head is being disengaged from recording operation. This recording method is to discharge ink on a recording sheet for recording in response to recording signals. It is widely used as a quiet recording method, which is operable at low running costs. Also, with a recording head in which many numbers of nozzles are arranged on a straight line for discharging ink in the sub-scanning direction, the recording is performed by one-time scan of the recording head on a recording sheet in a width that corresponds to the nozzle numbers. Therefore, it is possible to attain a higher speed recording.
Further, in a case of an ink jet recording apparatus capable of recording in colors, color images are formed by superposing ink droplets discharged from a plurality of recording heads for color use. In general, when a color recording is executed, it is required to prepare recording heads for the three primary colors, yellow (Y), magenta (M), and cyan (C) or four kinds of recording heads and ink cartridges for use of the three primary colors and one black (Bk). In recent years, the apparatuses, which are capable of forming images in full colors, have been practically in use by means of recording heads for three to four colors.
Moreover, it is comparatively easy for an ink jet recording apparatus of the kind to arrange its structure so that it can record on a large sheet in A-1 size. In other words, recording apparatuses, a printer for use of CAD output or some other plotters, for example, have been actually manufactured to execute color recording on a recording sheet of A-1 size. Here, a source document is copied on it by connecting an image reader to the ink jet recording apparatus. Also, there have been various demands on different uses of the recording apparatus of this type. Particularly, it has been increasingly required to make the apparatus capable of recording on OHP films that may be used for projection of presentations in conferences, lectures, or the like. In order to meet such demands, the development and production are being attempted to provide an apparatus capable of recording on a selected medium as desired in an excellent condition at any time, irrespective of the kinds of recording media having different characteristics of ink absorption, for example.
In addition, ink jet recording apparatuses are increasingly on demand in wider fields of industries (in an apparel industry or the like, for example) as an excellent recording means. Thus it is required still more to provide images in a higher quality.
In this respect, however, the conventional ink jet recording apparatuses present a problem as its drawback in some cases that ink runs out while in printing. More specifically, when an automatic sheet feeder is installed on a recording apparatus to execute printing on a plurality of recording sheets in succession by use of a continuous sheet feeding, for example, there is a possibility that ink is completely consumed while in printing (hereinafter referred to as "ink shortage"). Here, the following problems are also encountered. For example, unless the user is informed of such ink shortage, the time that is taken in printing after the "ink shortage" is just a waste. Also, the unclear printing continues in the so-called "scratchy letters" immediately before the ink shortage. As a result, a number of recording sheets are used wastefully in some cases.
Also, in an ink jet recording apparatus of bubble jet type using electrothermal transducing elements, not only the problems occur as described above, but those given below will take place. In other words, if the discharge heaters of the recording head are driven continuously in a state that no ink is present in the ink discharge ports, the recording head is caused to be overheated, leading to drawbacks such as deformation or damages brought to the recording head in some cases.
Therefore, in order to avoid such drawbacks, there have been invented various means for detecting ink shortage (means for detecting ink remains) in recent years. As means for detecting ink shortage, a structure has been proposed, for example, wherein an ink tank is formed by an elastic material, and then, the deformation of the ink tank, which takes place along the reduction of ink contained ink in it, is detected by a mechanical switch. Also, a method has been proposed, in which detection current flows across two electrodes installed dedicatedly therefor in positions directly in contact with ink in the ink tank so as to detect the resistance value across them for sensing the reduction of ink remains. Also, a method is known, in which discharged dot numbers are summed up and stored in order to estimate the accumulated amount of ink consumption and predict the time of ink shortage.
For the structure or methods described above, however, it is necessary to prepare the member dedicated to sensing the ink shortage. As a result, significant cost increase is inevitable, yet a problem is still encountered that the detection of ink shortage obtainable by the proposed structure or methods is not sufficiently precise.